1. Field of the Inventive Concept(s)
The presently disclosed and/or claimed inventive concept(s) relates generally to retro-aldol reaction products and methods of making and using same. More particularly, but without limitation, the methods disclosed herein for producing the retro-aldol reaction products are performed in a non-aqueous/solvent-free based process. The reaction products obtained from the process include, for example, dihydroxyacetone, glyceraldehyde, glycolaldehyde, and combinations thereof. In one particular embodiment, the process of making such retro-aldol reaction products includes, without limitation, the step of mechanocatalytically reacting a heterogeneous catalyst with one or more sugar reactants.
2. Background of the Inventive Concept(s)
The conversion of cellulosic biomass represents a potentially rich source of salable products such as glucose, dihydroxyacetone and glyceraldehyde. Markets for these biomass-based materials will expand as demand grows for non-petroleum sourced materials, for example. Current production methods utilize glycerol as a starting point. Profitability could be improved significantly by development of a scalable process using, for example, glucose or xylose as a starting point.
Dihydroxyacetone (“DHA”) is a versatile three carbon building block that is extremely useful in many organic synthesis routes. (Enders et al., “The Dihydroxyacetone Unit—A versatile C3 Building Block in Organic Synthesis,” Angew. Chem. Ind. 2005, 44, 1304-1325) DHA is a simple carbohydrate (i.e., a triose) having the formula C3H6O3. Currently, DHA itself is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as sugar beets and sugar cane, and by the fermentation of glycerin. DHA is a hygroscopic white crystalline powder and is the simplest of all ketoses and, having no chiral center, is the only ketose that has no optical activity. DHA is normally found as a dimer which is slowly soluble in an aqueous ethanol mixture. In its phosphate form, dihydroxyacetone phosphate (DHAP), it takes part in glycolysis and is an intermediate product of fructose metabolism.
Typically, DHA is prepared along with glyceraldehyde by the mild oxidation of glycerol with hydrogen peroxide and a ferrous salt as catalyst. It can also be prepared in high yield and selectivity at room temperature from glycerol using a cationic neocuproine-based palladium catalyst with oxygen or air acting as the co-oxidant. Although DHA is most commonly used as an ingredient in sunless tanning products, it has also been recognized as a key raw material for the production of specialty chemical products such as acrylic and cyclic derivatives. (See, e.g., Enders et al.) Glyceraldehyde is a structural isomer of dihydroxyacetone, i.e., a triose monosaccharide with the chemical formula C3H6O3, and it is the simplest of all common aldoses. The name “glyceraldehyde” comes from the combination of glycerine and aldehyde, as glyceraldehyde is merely glycerine with one hydroxymethylene group changed to an aldehyde.
Glycolaldehyde (HOCH2—CH—O) is the smallest possible molecule that contains both an aldehyde group and a hydroxyl group. It is the only possible diose, i.e., a 2-carbon monosaccharide. While not a true sugar, Glycoaldehyde is the simplest sugar-related molecule. Glycolaldehyde is an intermediate in the formose reaction. Glycolaldehyde is formed from many precursors, including the amino acid glycine. It can form by action of ketolase on fructose 1,6-bisphosphate in an alternate glycolysis pathway.
Mechanocatalysis or tribocatalysis is a solid-solid reaction using mechanical force without the addition of solvents, i.e., it is a non-aqueous or solvent-free catalytic reaction. Effective mechanocatalysts are mechanically robust, and possess sites that are physically accessible and chemically active. Mechanocatalytic processes also typically do not require external heat. Substantially all of the energy for the reaction comes from the pressures and frictional heating provided by the kinetic energy of milling media moving in a container. In a mechanocatalytic system, it is important that intimate contact between the catalyst and reactant is maintained. Pebble (or rolling) mills, shaker mills, attrition mills, and planetary mills are a few examples of mills that effectively “push” the catalyst into contact with the material to be treated in a mechanocatalytic process. A mechanocatalytic process for converting biomass to soluble sugars is, for example, disclosed in U.S. Ser. No. 11/935,712, the entire contents of which are hereby incorporated by reference in their entirety.
As such, disclosed and/or claimed herein are processes and methods for economically, safely, and reliably producing retro-aldol reaction products from the reaction of at least one sugar reactant with a heterogeneous catalyst. More particularly, but without limitation, the processes and methods claimed herein for producing retro-aldol reaction products are performed in a non-aqueous/solvent-free process. Also disclosed and/or claimed herein are reaction products from such a process that comprise at least one of dihydroxyacetone, glyceraldehyde, glycolaldehyde, and combinations thereof. In one particular embodiment, the process of making such retro-aldol reaction products includes, without limitation, the step of mechanocatalytically reacting at least one sugar reactant with a heterogeneous catalyst.